Strong and Stable Nanocomposites Prepared by High-Pressure Torsion of Cu-Coated Fe Powders

Abstract

Segregation and chemical inhomogeneity are well-known problems in powder metallurgy and are also an issue for new applications of powder mixtures, for example as starting materials for severe plastic deformation. In this study, Cu-coated Fe powder was prepared via immersion deposition, inductively hot-pressed and subsequently deformed using high-pressure torsion. The homogeneity of the pressed material was found to be much better than that of powder mixtures that were prepared for comparison. During severe plastic deformation, higher hardness was observed for the coated powder as compared to powder mixtures even after low strains. In the saturation state, the coated powder was found to result in a hardness of about 600 HV, which is significantly harder than for the powder mixtures. This is attributed to the greater amount of impurities introduced by the coating process. It is shown that coated powders are promising starting materials for severe plastic deformation in order to reduce the amount of strain necessary to reach the saturation state and to obtain high strength and more homogeneous mechanical alloying.

High-Pressure Torsion Deformation Induced Phase Transformations and Formations: New Material Combinations and Advanced Properties

“…In a first feasibility study, 123) Fe powders coated by a Cu layer of about 12 µm thickness were prepared by immersion deposition and subsequently inductively hot-pressed to obtain a pre-compacted starting material. For comparison, a mixture of elemental Fe and Cu powders with similar powder particle sizes and overall composition was pre-compacted in the same way as the coated powders.…”

“…The overlay illustrates EDX measurement areas with the color indicating the measured Cu contents in wt% in each area. 123) Another approach to prevent powder inhomogeneity would be the synthesis of pre-alloyed powders. With inert gas condensation, for example, the production of pure metals, alloys and oxides with average NC grain sizes, high purity and uniform nanostructures is possible.…”

Mechanical properties of aluminum matrix composite reinforced with titanium carbide

“…As a result of high-pressure torsion, the coating layered on aluminum particles breaks down into individual reinforcing titanium carbide particles, the size of which is determined by the thickness of the titanium carbide layers. This method not only achieves a uniform distribution of reinforcing nanosized particles over the volume and reduces porosity [10,11], but also grinds aluminum grains. In addition, reinforcing nanoparticles at the grain boundaries of the aluminum matrix prevent their fusion.…”